Genetic damage from smoking measured for the first time
Scientists establish link between number of cigarettes smoked and cell mutations. Also, type 2 diabetes related to number of ‘toxic’ ceramides, and cut belly fat by using canola oil
For the first time, scientists have measured the catastrophic genetic damage caused by smoking and have established a direct link between the number of cigarettes smoked in a lifetime and the number of mutations in the DNA of tumours. On average, smoking a pack of cigarettes a day led to 150 mutations in each lung cell every year. These mutations represent individual potential starting points for a cascade of genetic damage that can eventually lead to cancer.
The researchers at the Wellcome Trust Sanger Institute, the Los Alamos National Laboratory and other collaborators, studied over 5,000 tumours, comparing cancers from smokers with cancers from people who had never smoked. Smoking affected more than just the lungs. The study, published in the journal Science, found a pack a day led to an estimated average 97 mutations in each cell in the larynx, 39 mutations for the pharynx, 23 mutations for mouth, 18 mutations for bladder, and six mutations in every cell of the liver each year.
Professor David Phillips, an author on the paper and Professor of Environmental Carcinogenesis at King’s College London, says: “The results are a mixture of the expected and unexpected, and reveal a picture of direct and indirect effects. Mutations caused by direct DNA damage from carcinogens in tobacco were seen mainly in organs that come into direct contact with inhaled smoke. In contrast, other cells of the body suffered only indirect damage, as tobacco smoking seems to affect key mechanisms in these cells that in turn mutate DNA.”
The study revealed at least five distinct processes of DNA damage due to cigarette smoking. The most widespread of these is a mutational signature already found in all cancers. In this case, tobacco smoking seems to accelerate the speed of a cellular clock that mutates DNA prematurely.
Tobacco smoking claims the lives of at least six million people every year and, if current trends continue, the World Health Organisation predicts more than 1 billion tobacco-related deaths in this century.
Diabetes risk linked to ‘toxic fat’
Why do some thin people develop diabetes while some obese people don’t? A new study by an international team of scientists answers the riddle: accumulation of a toxic class of fat metabolites, known as ceramides, may make people more prone to type 2 diabetes.
“Ceramides impact the way the body handles nutrients,” explains the study’s senior author Scott Summers, chairman of the University of Utah’s Department of Nutrition and Integrative Physiology. “They impair the way the body responds to insulin, and also how it burns calories.”
When people overeat, they produce an excess of fatty acids. Those can be stored in the body as triglycerides or burned for energy. However, in some people, fatty acids are turned into ceramides. A build-up of ceramides prevents the normal function of fat (adipose) tissue. Fat spills out into the blood vessels or heart and does damage to other peripheral tissues.
The three-year project found that adding excess ceramides to human fat cells, or mice, caused them to become unresponsive to insulin and develop impairments in their ability to burn calories. The mice were also more susceptible to diabetes as well as fatty liver disease. Conversely, they also found that mice with fewer ceramides in their adipose tissue were protected from insulin resistance, a first sign of diabetes.
The trend may also hold true in people. In fact, among patients in Singapore receiving gastric bypass surgery, ceramide levels predicted who had diabetes better than obesity did. Even though all of the patients were obese, those who did not have type 2 diabetes had less ceramide in their adipose tissue than those who were diagnosed with the condition. The scientists are now searching for genetic mutations that lead to people’s predisposition to accumulating ceramides.
Trimming the spare tyre: cooking with canola oil may cut belly fat
Including canola oil in a healthy diet may help reduce abdominal fat in as little as four weeks, according to health researchers from Pennsylvania State University. After one month of adhering to diets that included canola oil, study participants had 110 grams less belly fat than they did before the diet. Weight lost from the mid-section did not redistribute elsewhere in the body.
“Visceral, or abdominal, fat increases the risk for cardiovascular disease, and is also associated with increased risk for conditions such as metabolic syndrome and diabetes,” says Penny Kris-Etherton, distinguished professor of nutrition at Penn State. “Monounsaturated fats in canola oil decrease this fat that has adverse health effects.”
In order to incorporate canola oil into the diet, Kris-Etherton suggests using it when sautéing foods, in baking, adding it to a smoothie and in salad dressings.
The researchers tested the effect of five different vegetable oil blends in 101 participants’ diets by incorporating the oil into two smoothies drunk each day. All of the participants had abdominal obesity, or increased waist circumference, and were either at risk for or had metabolic syndrome. The subjects were randomly assigned to follow for four weeks each of the treatment oil diets: conventional canola, high-oleic acid canola, high-oleic acid canola with DHA (a type of omega-3 fatty acid), corn/safflower and flax/safflower. After each four-week diet period, participants were given a four-week break before starting the next diet period.
